New vistas for alpha-frequency band oscillations.

The amplitude of alpha-frequency band (8-14 Hz) activity in the human electroencephalogram is suppressed by eye opening, visual stimuli and visual scanning, whereas it is enhanced during internal tasks, such as mental calculation and working memory. alpha-Frequency band oscillations have hence been thought to reflect idling or inhibition of task-irrelevant cortical areas. However, recent data on alpha-amplitude and, in particular, alpha-phase dynamics posit a direct and active role for alpha-frequency band rhythmicity in the mechanisms of attention and consciousness. We propose that simultaneous alpha-, beta- (14-30 Hz) and gamma- (30-70 Hz) frequency band oscillations are required for unified cognitive operations, and hypothesize that cross-frequency phase synchrony between alpha, beta and gamma oscillations coordinates the selection and maintenance of neuronal object representations during working memory, perception and consciousness.